System of control for electric motors.



No. 808,729 PATENTED JAN. 2, 1906. M. W. DAY.

SYSTEM OF CONTROL FOB. ELECTRIC MOTORS.

APPLIGATION FILED MAY15, 1905.

Witnesses. Inventor:

M/ Maxweli W. Dag, #Z W 9 fit 1 4 UNITED STATES PATENT OFFICE.

MAXWELL W. DAY, OF SCHEN ECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF CONTROL FOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented Jan. 2, 1906.

Application filed May 15, 1905. Serial No. 260.427.

To all whmn it nun; 0071102772 Be it known that I, MAXWELL W. DAY, acitizen of the United States, residing at Schenectady, county ofSchenectady, State of New York, have invented certain new and usefulImprovements in Systems of Control for Electric Motors, of which thefollowing is a speci fication.

The present invention relates to systems of control for electric motors,and particularly for motors employed for operating hoists or similarapparatus.

In my prior patent, No. 589,891, granted September 14, 1897, thereis'disclosed a system of control for simple shunt-wound motors soarranged as to propel the load in either direction, or if the load issufficiently heavy enabling the motor to act as a generator for thepurpose of producing a braking effect. For many purposes the shunt-woundmotor is entirely satisfactory; but where the time factor is of theutmost importanceas, for example, in the case ofammunitionhoistscompoundwound motors are more suitable, they being byreason of the saving in current effected and the consequent reduction inheating the apparatus better adapted for rapid acceleration. Diflicultyhas been experienced in attempting to so adapt compound-wound motors,for the reason that in some stages of operation objectionable fieldconditions are obtained.

The object of the present invention is to provide means for controllinga compoundwound motor in such a manner that it may operate to goodadvantage in propelling a load in either direction or in acting as abraking-generator driven by the load.

To the above end I divide the series fieldwindings of the motor into twohalves which when the motor is raising the load assist the shunt-windingto excite the field, when the motor is lowering a light load oppose eachother, but in the aggregate assist the shuntwinding, and when the motoris overhauled by the load and becomes a generator assist theshunt-winding.

A full understanding of the present inven tion in its various aspectsmay be had from the following detailed description, aided by theaccompanying drawings, which illustrate one form thereof.

In the drawings, Figure 1 is a diagramnatic representation of a hoistingsystem arranged in accordance with the present invention. Figs. 2 and 3show certain motor connections when the motor is raising a load. Figs.4, 5, and 6 show certain motor connections when the motor is acting as agenerator, andFigs. 7, 8, and 9 are views similar to Figs. 4, 5, and 6,but showing the direction of current when the motor is acting as a motorto lower a light load.

Similar reference characters will be used throughout the specificationand drawings to denote like parts.

Reference being had to Fig. 1, M indicates a motor having an armature A,the shunt fieldwinding B and the series field-winding made up of thecoils C and D. The motor is geared to the cable-drum E, which raises andlowers the cage or load W. K is a motor controller which consists of therow of fixed contacts 1 to 10, inclusive, and the two sets of movablecontacts F and G. R is the resistance to which the fixed contacts 1 to 7are connected. The shunt-winding B is connected directly across thesupply-mains l and 1 when the switch S is closed and is thereforeindependent of the controller. When the controller is in its inoperativeor off position, the motor-armature and the field-coil. D areshort-circuited by means of the auxiliary contacts 7c and it, whichengage the fixed contacts 8 and 9 only in that position of thecontroller, this being substantially the arrangement shown in myaforesaid patent, except that in said patent the series field-coil isnot present.

When it is desired to raise the cage or weight WV, the switch S isclosed and the con troller is turned so as to bring the contacts F intoengagement with the row of fixed contacts. The short circuit produced bythe auxiliary contacts 76 and 7c is broken, and the motor is connectedtoline with a portion of resistance in circuit with the armature andseries field-coils, as indicated in Fig. 2. As the movement of thecontroller is continued the resistance is cut out step by step until themotor is connected directly across the line, as in Fig. 3. The flow ofcurrent is the usual one for compound-wound motorsnamely,

der other conditions, as will appear hereinafter. Upon returning thecontroller to its off position the auxiliary contacts 76 and 7cshort-circuit the armature, causing the mo' tor to act as a brake tobring the load to rest.

In order to lower the load, the controller is turned in the oppositedirection, bringing the contacts G into engagement with the row of fixedcontacts, and thereby connecting the motor for operation in the reversedirection. The motor connections for lowering are when the controller isin its first lowering position those shown in Figs. 4 and 7namely, themotor-armature and the series coil D are short-circuited, while theseries coil C is connected across the line in series with the re-.

sistance B. As the movement of the controller is continued the armatureand fieldcoil D are shunted across increasing amounts of the resistanceuntil finally the armature and the coil D are arranged in shunt with theentire resistance.

If the load is light, so that it is insufficient to overcome thefriction, and therefore requires power to make it descend, current issupplied from the mains to the field and the armature of the motor andflows in the direction of the arrows in Figs. 7, .8, and 9. In Fig. 7practically no current flows from the line through the armature and theseries coil D but as the controller is moved to succeeding positions thearmature and the series coil D are supplied with current in multiple,with increasing portions of the resistance until finally, as illustratedin Fig. 9, the armature and the field-coil D are in multiple with theentire resistance. It will be noted that whenever current flows throughthe coil D of the series winding in lowering a light load the excitationproduced by this coil is opposed to that produced by the excitation ofthe other series coil C. The current which flows through the coil C isalways greater than that which fiows through the coil D, since it is thesum of the current which passes through the resistance and that whichpasses through the coil D. Therefore although the series coils opposeeach other their aggregate effect is to produce an excitation cumulativeto the excitation of the shunt-field, and since no great amount of poweris required to propel light loads in their descent the motor as thusconnected fulfils all requirements. If the entire series windings wereplaced at C, it would assist the shuntwinding, producing a very strongfield, at a time, however, when it is not needed. If, on the other hand,the series windings were both placed at D, they would oppose theshuntwinding, and by reason of the proportions usually adopted in motorsperforming this class of work the shunt-field winding would become tooweak.

In Figs. 4, 5, and 6 the motor connections are the same as those shownin Figs. 7, 8, and

9 but the directions of the currents are those which take place when thedescending load is heavy and is overhauling the motor, thereby causingit to act as a generator to retard the movement of the load. In Fig. 4the maximum braking effect is produced, since the current generated inthe shortcircuited armature produces an excitation in the seriesfield-coil D, which assists the excitation of the coils B and C. Theload will therefore descend very slowly as long as the controller isleft in its first lowering position. As the controller is moved intosuccessive running positions varying portions of the resistance areincluded in the circuit of the armature and field-coil D. .Thisincreases the resistance of the armature-circuit and permits the motorto run at a higher rate of speed. A point will be reached, however, asin Fig. 5, at which potential produced by the motor operating thegenerator will equal the line potential. At that point no current passesthrough the resistance from one main to the other, and consequently thefield-coil C becomes idle. In the final position, Fig. 6, the motor maybe sending current back into the line, in which case current will flowthrough the field-coil C in the opposite direction from that whichpassed during the preceding positions of the controller, and thereforethe total field will be weaker than at any previous stage. By this meansthe descending load is kept under perfect control and the rapidity ofdescent may be regulated. Were both series windings placed at C, theywould assist the shunt-winding in the initial position. YVith a heavyload, however, the cumulative effect would be less than with thearrangement shown, since more current passes through D than C. As soonas the motor began returning current to the line the series windingwould oppose the shunt-winding, bringing the field below the normalfield produced by the shunt-winding alone. If desired, the shuntfield-winding may be connected to the opposite end of the series windingfrom that shown.

It will now be seen that by the present i11- vention the motorconnections are so arranged that desirable and effective results areproduced, not only under certain of the conditions to be met in theoperation of hoists or elevators, but in all of them, and under nocondition is the motor-field weakened below the point at which theshunt-field alone would maintain it-namely, the motor is provided with apowerful field for raising loadswith a weaker field, but one quitestrong enough for propelling light loads downward and for retarding thedescent of a heavy load.

Although I have described the present invention in great detail asembodied in a preferred form, it is of course understood that manychanges may be made in the arrangement of the field-windings and themanner of and means for connecting them in order to produce the desiredresults.

In the appended claims I aim to cover all modifications Within thespirit of the present invention.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. In a system of control, a motor having a shunt field-winding and aplurality of series field-windings, and means for connecting said motorto a source of current-supply in such a manner that the effectiveexcitation of the series windings assists that of the shunt-winding bothwhen the motor is propelling a load and when it is overhauled by theload and acting as a generator.

2. In a system of control, a motor having a shunt field-winding and aplurality of se ries field windings, means for connecting said motor toa source of supply in such a manner that the motor will run in onedirection and the field-windings will assist each other and theshunt-winding in exciting the field, and means for connecting the motorfor operation in the reverse direction in such a manner that theefiective excitation of the series windings is cumulative to that of theshunt-winding both when the motor is oper ating as a motor and when itis overhauled by the load and made to operate as a generator.

3. In a system of motor control, a motor having a shunt field-windingand a plurality of series field-windings, means for connecting the motorto a source of current-supply in such a manner that the shunt and serieswindings assist each other, and means for connecting the motor foroperation in the reverse direction in such a manner that the currentsflowing through the series windings are unequal and have opposingeffects which in the aggregate assist the shunt-winding, the arran ementbeing such that when the load over auls the motor and causes it to runas a generator the a gregate effect of the series windings is cumu ativeto that of the shunt-winding.

4. In a system of control, a motor having a plurality of serieswindings, means for connecting the motor to a source of current-sup plyso that the said field-windings assist each other when the motor runs inone direction, and means for connecting said motor for operation in thereverse direction in such a man-v ner that the field-windings opposeeach other when the motor is acting as a motor and assist each otherwhen the motor is overhauled by the load and is acting as a generator.

5. In a system of control, a motor having a shunt field-winding and aplurality of series field-windings, means for connecting the motor to asource of current-supply so that the said series field-windings assisteach other and the shunt-winding when the motor is operated in onedirection, and means for connecting said motor for operation in the repthe motor is acting as a motor and assist each other and theshunt-winding when the motor is overhauled by the load and acts as agenerator.

6. In a system of control, a motor having a shunt field-winding and aplurality of series field-windings, means for connecting the motor to asource of current-supply so that the series windings assist saidshuntwind ing when the motor runs in one direction, and means forconnecting a portion of said series field-windings to the source ofcurrentsupply and short-circuiting the motor-armature through theremainder of the series windings when the motor is connected foroperation in the reverse direction, whereby the shunt-winding isassisted by one or more of the series windings both when the motor isacting as a motor and when it is overhauled by the load and acts as agenerator.

7. In a system of motor control, a motor having a shunt field-windingand a plurality of series field windings, means for connecting saidmotor to a source of current-supply for rotation in one direction insuch a manner that the series field-windings assist each other and theshunt-winding, and means for connecting the motor for rotation in theopposite direction in such a manner that the relative effects of thewindings are changed.

8. In a system of control, a motor having a plurality of field-windings,and a controller having contacts constructed and arranged to connectsaid motor to a source of currentsupply with the field-windings arrangedin series with each other and with the armature, the contacts being alsoconstructed and arranged to connect a portion of said fieldwindings as ashunt-winding and short-circuit the armature through the remainingportion of the field-windings.

9. In a system of control, a motor having a plurality of field-windings,a resistance, and a controller having contacts and connectionsconstructed and arranged to connect said motor to a source ofcurrent-supply so that the field-windings are in series with each otherand with the armature when the motor runs in one direction, or so thatthe motor tends to run in the opposite direction and the armature isshort-circuited through a portion of the windings while the otherportion is connected with the source of current-supply through theresistance.

10. In a system of control, a motor having a shunt field-winding and aplurality of series field-windings, and a controller having contacts andconnections arranged to connect said motor to a source of current-supplyfor rotation in one direction, said controller also having contactsconstructed and arranged to connect the motor for rotation in theopposite direction with one of its series windings connected to thesource of currentsupply and with the armature short-circuited throughthe remainder of the series windings.

11. In a system of control, a motor having a plurality of field-win dings, a resistance, and a controller having contacts and connectionsconstructed and arranged to connect said motor to a source ofcurrent-supply so that the field-windings are in series with each otherand with the armature when the motor runs in one direction, and alsohaving contacts arranged to connect a portion of said series windings tothe source of current-sup ply in series with said resistance and to connect the armature and the remainder of the field-windings in shunt witha portion of said resistance.

12. In a system of control, a motor having a plurality of seriesfield-windings and a shunt field-winding, a resistance, and a controllerfor connecting said motor to a source of current-supply with thearmature in series with the series winding and in parallel with theshunt-winding for rotation in one direction, said controller havingcontacts connected and arranged to connect the motor for rotation in theopposite direction with a portion of the series windings connected tothe source of supply in series with the resistance and themotor-armature and the remainder of the series windings connected inshunt to variable portions of said resistance.

13. In a system of control, a motor having two field-windings, aresistance, and a controller having contacts constructed and arranged toconnect said motor to a source of current-supply with the field-windingsin series with the armature, said contacts being also constructed andarranged to connect one of said field-windings to the source ofourrent-supply in series with the resistance and. to short-circuit thearmature through the other field-windin in one position of thecontroller and to connect the armature and the latter field windin g inshunt with successively varying portions of said resistance insubsequent positions of the controller.

14. In a system of control, a motor having a shunt field-winding and twoseries lieldwindings, a resistance, and a controller having contacts andconnections constructed and arranged to connect said motor to a sourceof current-supply with the armature and series field-windings in serieswith. each other and in parallel with the shunt lieldwinding, saidcontroller also having contacts arranged to connect said motor to asource of current-simply with one series winding in series with theresistance and in parallel with the shunt-winding and the armatureshortcircuited through the other series winding in one position of thecontroller and with the armature and said latter field-winding shuntedacross varying portions of said resistance in subsequent positions ofthe controller.

In witness whereof I have hereunto set my hand this 12th day oi May,1905.

MAXI WELL W. DAY. IVitnesscs:

BENJAMIN B. HULL, HELEN ORFORD.

